Expressions

TemplateDX expressions run inside {...} braces or JSX attributes (<If condition={...}>). The evaluator supports a deliberately limited JavaScript subset: literals, property access, a fixed set of operators, and calls to registered filters.

Literals

Literal	Example
Strings	`"How are you?"`, `'How are you?'`
Numbers	`40`, `30.123`
Arrays	`[1, 2, "array"]`
Objects	`{ one: 1, two: 2 }`
Booleans	`true`, `false`

All five forms render in {} and work anywhere an expression is valid:

{props.tags.length}         {/* renders the number of tags */}
{[1, 2, 3].length}          {/* renders 3 */}

Property access

Read nested properties with dot notation or bracket syntax:

{props.user.name}
{props['user-email']}
{props.items[0].title}

Missing nested keys via MemberExpression render as empty string; see Variables for details.

Operators

Arithmetic

{ 2 + 3 }     {/* 5  */}
{ 10 - 4 }    {/* 6  */}
{ 10 / 2 }    {/* 5  */}
{ 10 % 3 }    {/* 1  */}
{ 5 * 4 }     {/* 20 */}

+ also concatenates strings: {"Hi " + props.name}.

Comparisons

Operator	Description
`==`	Loose equality
`!=`	Loose inequality
`>`	Greater than
`>=`	Greater than or equal
`<`	Less than
`<=`	Less than or equal

Strict equality (=== / !==) isn’t supported. Only the loose operators above are in the evaluator’s operator table. Use == / !=.

<If condition={props.numUsers > 10}>
  Content for more than 10 users
</If>

<If condition={props.score >= 75}>
  Content for scores 75 and above
</If>

Logical

<If condition={props.isActive && props.hasAccess}>
  Content for active users with access
</If>

<If condition={props.isAdmin || props.isModerator}>
  Content for admins or moderators
</If>

<If condition={!props.isBanned}>
  Content for users who are not banned
</If>

Filter calls

The only function calls allowed inside expressions are calls to registered filters:

{ upper(props.name) }          {/* ALICE */}
{ truncate(props.bio, 100) }   {/* first 100 chars + "..." */}

Method calls (props.name.toUpperCase()) throw at render time. The evaluator’s CallExpression handler explicitly rejects anything that isn’t a registered filter. Use the upper filter instead.

Example usage

<If condition={(props.age >= 18 && props.isMember) || props.hasGuestPass}>
  Welcome to the event!
</If>
<ElseIf condition={props.age >= 18 && !props.isMember}>
  Please consider becoming a member to enjoy full benefits.
</ElseIf>
<Else>
  Sorry, you must be at least 18 years old to attend.
</Else>

This branches on three conditions: adult members or guest-pass holders get a welcome; adult non-members get a prompt to join; the prompt tells everyone else they can’t attend.

Next steps

Filters are the only callables in expressions. See Filters for the built-in set and how to register your own.

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Reference

Literals

Property access

Operators

Arithmetic

Comparisons

Logical

Filter calls

Example usage

Next steps

​Literals

​Property access

​Operators

​Arithmetic

​Comparisons

​Logical

​Filter calls

​Example usage

​Next steps

Literals

Property access

Operators

Arithmetic

Comparisons

Logical

Filter calls

Example usage

Next steps